Doctor experience?

That's a good question. New oncologists work for a long time under supervision as interns or residents (analogous to apprentices and journeymen in the skilled trades).

In a big cancer centre, they will have participated in each common procedure dozens or hundreds of times, with increasing responsibility and autonomy, before heading their own teams of interns and residents.

They might or might not have had the same opportunities in a smaller, non-specialised hospital.

"done" could also include "assisted" or just plain old watched. It doesn't matter. They've been there, done that.
It's a team in the room doing it.
Training & experience is training & experience.
It's all good.

They usually train under experienced surgeons for years.
My surgeon, for instance:
"David's basic urology training was undertaken in New Zealand. Upon completion of his training he undertook a one year fellowship in Cambridge, UK, under Professor David Neal. Here he studied major open urological surgery with an emphasis on pelvic cancer (bladder and prostate) and kidney cancer. David also trained in Cambridge in advanced and complex testicular cancer."

You can tell how many they've done by how grey their hair is.

some what related, I had kidney stones removed, (2nd time) when it got time to remove the tube, the doctor asked what I assumed was a student if she wanted to remove the tube, I mentioned to him that the last time I had it done, it felt like someone hit me with a bat, he said well then hang on, she did a wonderful job, yank fast, lol. Point is, I understand they all have to learn, otherwise we run out of trained specialists. Them knowing more than me about what they doing shouldn't be too hard a reach. Best to all.

So true, Scott. When my RO told me he was 34 yrs old I almost ran out the door! But I quickly calmed down when I remembered that he had authored 4 clinical papers directly dealing with prostate cancer and outcomes.
I also reflected on my own history as a dentist. Two or three years out of school I was hands down light years ahead of all the “older” practitioners in my area. I’m Not bragging; they were so bad! They were completely out of touch with newer techniques and their views on how to treat certain things like gum disease or root canal were from the Stone Age!
I shudder to say it but don’t think oncology doesn’t have its share of dinosaurs who are still treating this disease like they did decades ago.